impl Clone for Cow
Back io::stdin with a global singleton BufferedReader

io::stdin returns a new `BufferedReader` each time it's called, which
results in some very confusing behavior with disappearing output. It now
returns a `StdinReader`, which wraps a global singleton
`Arc<Mutex<BufferedReader<StdReader>>`. `Reader` is implemented directly
on `StdinReader`. However, `Buffer` is not, as the `fill_buf` method is
fundamentaly un-thread safe. A `lock` method is defined on `StdinReader`
which returns a smart pointer wrapping the underlying `BufferedReader`
while guaranteeing mutual exclusion.

Code that treats the return value of io::stdin as implementing `Buffer`
will break. Add a call to `lock`:

```rust
io::stdin().lines()
// =>
io::stdin().lock().lines()
```

Closes #14434

[breaking-change]
libstd/sys/unix/process.rs: reap a zombie who didn't get through to exec(2).

After the library successfully called fork(2), the child does several
setup works such as setting UID, GID and current directory before it
calls exec(2).  When those setup works failed, the child exits but the
parent didn't call waitpid(2) and left it as a zombie.

This patch also add several sanity checks.  They shouldn't make any
noticeable impact to runtime performance.

The new test case run-pass/wait-forked-but-failed-child.rs calls the ps
command to check if the new code can really reap a zombie.  When
I intentionally create many zombies with my test program
./spawn-failure, The output of "ps -A -o pid,sid,command" should look
like this:

  PID   SID COMMAND
    1     1 /sbin/init
    2     0 [kthreadd]
    3     0 [ksoftirqd/0]
...
12562  9237 ./spawn-failure
12563  9237 [spawn-failure] <defunct>
12564  9237 [spawn-failure] <defunct>
...
12592  9237 [spawn-failure] <defunct>
12593  9237 ps -A -o pid,sid,command
12884 12884 /bin/zsh
12922 12922 /bin/zsh
...

Filtering the output with the "SID" (session ID) column is a quick way
to tell if a process (zombie) was spawned by my own test program.  Then
the number of "defunct" lines is the number of zombie children.

Signed-off-by: NODA, Kai <nodakai@gmail.com>
Make missing_doc lint check typedefs

Closes #19543
std: Close TcpListener with closesocket()

This may have inadvertently switched during the runtime overhaul, so this
switches TcpListener back to using sockets instead of file descriptors. This
also renames a bunch of variables called `fd` to `socket` to clearly show that
it's not a file descriptor.

Closes #19333
std: Rewrite the `sync` module

This commit is a reimplementation of `std::sync` to be based on the
system-provided primitives wherever possible. The previous implementation was
fundamentally built on top of channels, and as part of the runtime reform it has
become clear that this is not the level of abstraction that the standard level
should be providing. This rewrite aims to provide as thin of a shim as possible
on top of the system primitives in order to make them safe.

The overall interface of the `std::sync` module has in general not changed, but
there are a few important distinctions, highlighted below:

* The condition variable type, `Condvar`, has been separated out of a `Mutex`.
  A condition variable is now an entirely separate type. This separation
  benefits users who only use one mutex, and provides a clearer distinction of
  who's responsible for managing condition variables (the application).

* All of `Condvar`, `Mutex`, and `RWLock` are now directly built on top of
  system primitives rather than using a custom implementation. The `Once`,
  `Barrier`, and `Semaphore` types are still built upon these abstractions of
  the system primitives.

* The `Condvar`, `Mutex`, and `RWLock` types all have a new static type and
  constant initializer corresponding to them. These are provided primarily for C
  FFI interoperation, but are often useful to otherwise simply have a global
  lock. The types, however, will leak memory unless `destroy()` is called on
  them, which is clearly documented.

* The `Condvar` implementation for an `RWLock` write lock has been removed. This
  may be added back in the future with a userspace implementation, but this
  commit is focused on exposing the system primitives first.

* The fundamental architecture of this design is to provide two separate layers.
  The first layer is that exposed by `sys_common` which is a cross-platform
  bare-metal abstraction of the system synchronization primitives. No attempt is
  made at making this layer safe, and it is quite unsafe to use! It is currently
  not exported as part of the API of the standard library, but the stabilization
  of the `sys` module will ensure that these will be exposed in time. The
  purpose of this layer is to provide the core cross-platform abstractions if
  necessary to implementors.

  The second layer is the layer provided by `std::sync` which is intended to be
  the thinnest possible layer on top of `sys_common` which is entirely safe to
  use. There are a few concerns which need to be addressed when making these
  system primitives safe:

    * Once used, the OS primitives can never be **moved**. This means that they
      essentially need to have a stable address. The static primitives use
      `&'static self` to enforce this, and the non-static primitives all use a
      `Box` to provide this guarantee.

    * Poisoning is leveraged to ensure that invalid data is not accessible from
      other tasks after one has panicked.

  In addition to these overall blanket safety limitations, each primitive has a
  few restrictions of its own:

    * Mutexes and rwlocks can only be unlocked from the same thread that they
      were locked by. This is achieved through RAII lock guards which cannot be
      sent across threads.

    * Mutexes and rwlocks can only be unlocked if they were previously locked.
      This is achieved by not exposing an unlocking method.

    * A condition variable can only be waited on with a locked mutex. This is
      achieved by requiring a `MutexGuard` in the `wait()` method.

    * A condition variable cannot be used concurrently with more than one mutex.
      This is guaranteed by dynamically binding a condition variable to
      precisely one mutex for its entire lifecycle. This restriction may be able
      to be relaxed in the future (a mutex is unbound when no threads are
      waiting on the condvar), but for now it is sufficient to guarantee safety.

* Condvars now support timeouts for their blocking operations. The
  implementation for these operations is provided by the system.

Due to the modification of the `Condvar` API, removal of the `std::sync::mutex`
API, and reimplementation, this is a breaking change. Most code should be fairly
easy to port using the examples in the documentation of these primitives.

[breaking-change]

Closes #17094
Closes #18003
auto merge of #19362 : nikomatsakis/rust/crateification, r=nikomatsakis

This has the goal of further reducing peak memory usage and enabling more parallelism. This patch should allow trans/typeck to build in parallel. The plan is to proceed by moving as many additional passes as possible into distinct crates that lay alongside typeck/trans. Basically, the idea is that there is the `rustc` crate which defines the common data structures shared between passes. Individual passes then go into their own crates. Finally, the `rustc_driver` crate knits it all together.

cc @jakub-: One wrinkle is the diagnostics plugin. Currently, it assumes all diagnostics are defined and used within one crate in order to track what is used and what is duplicated. I had to disable this. We'll have to find an alternate strategy, but I wasn't sure what was best so decided to just disable the duplicate checking for now.
auto merge of #19334 : alexcrichton/rust/issue-19333, r=aturon

This may have inadvertently switched during the runtime overhaul, so this
switches TcpListener back to using sockets instead of file descriptors. This
also renames a bunch of variables called `fd` to `socket` to clearly show that
it's not a file descriptor.

Closes #19333
Fall out of the std::sync rewrite
rollup merge of #19274: alexcrichton/rewrite-sync

This commit is a reimplementation of `std::sync` to be based on the
system-provided primitives wherever possible. The previous implementation was
fundamentally built on top of channels, and as part of the runtime reform it has
become clear that this is not the level of abstraction that the standard level
should be providing. This rewrite aims to provide as thin of a shim as possible
on top of the system primitives in order to make them safe.

The overall interface of the `std::sync` module has in general not changed, but
there are a few important distinctions, highlighted below:

* The condition variable type, `Condvar`, has been separated out of a `Mutex`.
  A condition variable is now an entirely separate type. This separation
  benefits users who only use one mutex, and provides a clearer distinction of
  who's responsible for managing condition variables (the application).

* All of `Condvar`, `Mutex`, and `RWLock` are now directly built on top of
  system primitives rather than using a custom implementation. The `Once`,
  `Barrier`, and `Semaphore` types are still built upon these abstractions of
  the system primitives.

* The `Condvar`, `Mutex`, and `RWLock` types all have a new static type and
  constant initializer corresponding to them. These are provided primarily for C
  FFI interoperation, but are often useful to otherwise simply have a global
  lock. The types, however, will leak memory unless `destroy()` is called on
  them, which is clearly documented.

* The fundamental architecture of this design is to provide two separate layers.
  The first layer is that exposed by `sys_common` which is a cross-platform
  bare-metal abstraction of the system synchronization primitives. No attempt is
  made at making this layer safe, and it is quite unsafe to use! It is currently
  not exported as part of the API of the standard library, but the stabilization
  of the `sys` module will ensure that these will be exposed in time. The
  purpose of this layer is to provide the core cross-platform abstractions if
  necessary to implementors.

  The second layer is the layer provided by `std::sync` which is intended to be
  the thinnest possible layer on top of `sys_common` which is entirely safe to
  use. There are a few concerns which need to be addressed when making these
  system primitives safe:

    * Once used, the OS primitives can never be **moved**. This means that they
      essentially need to have a stable address. The static primitives use
      `&'static self` to enforce this, and the non-static primitives all use a
      `Box` to provide this guarantee.

    * Poisoning is leveraged to ensure that invalid data is not accessible from
      other tasks after one has panicked.

  In addition to these overall blanket safety limitations, each primitive has a
  few restrictions of its own:

    * Mutexes and rwlocks can only be unlocked from the same thread that they
      were locked by. This is achieved through RAII lock guards which cannot be
      sent across threads.

    * Mutexes and rwlocks can only be unlocked if they were previously locked.
      This is achieved by not exposing an unlocking method.

    * A condition variable can only be waited on with a locked mutex. This is
      achieved by requiring a `MutexGuard` in the `wait()` method.

    * A condition variable cannot be used concurrently with more than one mutex.
      This is guaranteed by dynamically binding a condition variable to
      precisely one mutex for its entire lifecycle. This restriction may be able
      to be relaxed in the future (a mutex is unbound when no threads are
      waiting on the condvar), but for now it is sufficient to guarantee safety.

* Condvars support timeouts for their blocking operations. The
  implementation for these operations is provided by the system.

Due to the modification of the `Condvar` API, removal of the `std::sync::mutex`
API, and reimplementation, this is a breaking change. Most code should be fairly
easy to port using the examples in the documentation of these primitives.

[breaking-change]

Closes #17094
Closes #18003
rollup merge of #19359: japaric/clone-cow

Now we can use `#[deriving(Clone)]` on structs that contain `Cow`.

r? @aturon or anyone else
rollup merge of #19364: steveklabnik/doc_buffered_reader

We don't need this &mut, and vec could use []s
rollup merge of #19386: tbu-/pr_refcell_stuff
rollup merge of #19387: jauhien/fix-expand_quote_ty

Subj., expand_quote_ty produces wrong call to parse_ty now.
rollup merge of #19396: kulakowski/patch-1
rollup merge of #19413: P1start/more-trailing-commas

The only other place I know of that doesn’t allow trailing commas is closure types (#19414), and those are a bit tricky to fix (I suspect it might be impossible without infinite lookahead) so I didn’t implement that in this patch. There are other issues surrounding closure type parsing anyway, in particular #19410.
rollup merge of #19416: sfackler/global-stdin

io::stdin returns a new `BufferedReader` each time it's called, which
results in some very confusing behavior with disappearing output. It now
returns a `StdinReader`, which wraps a global singleton
`Arc<Mutex<BufferedReader<StdReader>>`. `Reader` is implemented directly
on `StdinReader`. However, `Buffer` is not, as the `fill_buf` method is
fundamentaly un-thread safe. A `lock` method is defined on `StdinReader`
which returns a smart pointer wrapping the underlying `BufferedReader`
while guaranteeing mutual exclusion.

Code that treats the return value of io::stdin as implementing `Buffer`
will break. Add a call to `lock`:

```rust
io::stdin().read_line();
// =>
io::stdin().lock().read_line();
```

Closes #14434

[breaking-change]
rollup merge of #19422: scialex/fix-fmt-macro-doc

these are missing standard #![doc(...)]. add them
rollup merge of #19453: pshc/rustdoc-check-a-href

Fixes the JS error in #18354 at least. I don't know if there's a more underlying issue that needs addressing.
rollup merge of #19454: nodakai/libstd-reap-failed-child

After the library successfully called `fork(2)`, the child does several
setup works such as setting UID, GID and current directory before it
calls `exec(2)`.  When those setup works failed, the child exits but the
parent didn't call `waitpid(2)` and left it as a zombie.

This patch also add several sanity checks.  They shouldn't make any
noticeable impact to runtime performance.

The new test case in `libstd/io/process.rs` calls the ps command to check
if the new code can really reap a zombie.
The output of `ps -A -o pid,sid,command` should look like this:

```
  PID   SID COMMAND
    1     1 /sbin/init
    2     0 [kthreadd]
    3     0 [ksoftirqd/0]
...
12562  9237 ./spawn-failure
12563  9237 [spawn-failure] <defunct>
12564  9237 [spawn-failure] <defunct>
...
12592  9237 [spawn-failure] <defunct>
12593  9237 ps -A -o pid,sid,command
12884 12884 /bin/zsh
12922 12922 /bin/zsh
...
```

where `./spawn-failure` is my test program which intentionally leaves many
zombies.  Filtering the output with the "SID" (session ID) column is
a quick way to tell if a process (zombie) was spawned by my own test
program.  Then the number of "defunct" lines is the number of zombie
children.